Use adaptive matching rules for tag search box

[yawitz]

As a result of the discussion in #401, starting at https://github.com/marklogic/marklogic-samplestack/issues/401#issuecomment-70924303, I'd like to propose a change to the behavior of the tag search box.

In the current design, the suggestion list includes all tags that contain the search string, even if the search string contains 1 char. I propose that we apply a different matching rule depending on the length of the search string:

• If the char count was, say <= 2, only include matches that start with the string.
• Otherwise include matches that include the string anywhere.

In fact, this approach could be generalized to any search box that includes an associated suggestion list dropdown.